Fluid hose

Abstract

Provided is a fluid hose having excellent ozone resistance and extraction resistance. Provided is a fluid hose comprising a nitrile rubber composition mainly composed of a nitrile rubber (A), the nitrile rubber composition having a modulus (M10) of 0.1-0.5 MPa, and the nitrile rubber composition not containing a paraffin wax.

Description

Technical Field

[0001] The present invention relates to a hose for fluids, and more particularly, to a hose for fluids having excellent ozone resistance and extraction resistance. Background Art

[0002] Although diene rubbers are relatively excellent in abrasion resistance, they are poor in weather resistance, especially ozone resistance, and their deterioration is accelerated in the presence of ozone, resulting in cracks, so-called ozone cracks, on the surface. These cracks are aggravated by the static stress and dynamic stress involved in rubber articles, and as a result, the rubber articles are damaged.

[0003] It is known to add wax to impart ozone resistance to the diene rubber.

[0004] For example, Patent Document 1 discloses a rubber composition for hose covering, which contains a diene polymer, a higher fatty acid ester having a melting point of 40°C or higher, a microcrystalline wax having 40 or more and 50 or less carbon atoms, and a paraffin wax having 30 or more and less than 40 carbon atoms.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Laid-Open No. 11-199711 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] However, when the rubber composition for hose covering disclosed in Patent Document 1 is used as a hose for liquids and a specific solvent (for example, a low molecular weight oil) is transported, there is a risk that the paraffin wax is extracted (dissolved) into the solvent.

[0010] On the other hand, when the paraffin wax is removed to suppress the extraction of components, there is a risk that sufficient ozone resistance cannot be obtained.

[0011] The present invention has been completed in view of such circumstances, and provides a hose for fluids having excellent ozone resistance and extraction resistance.

[0012] Means for Solving the Problems

[0013] In order to solve the above problems, the inventors of the present invention repeatedly conducted research and found that if a nitrile rubber is selected as the diene rubber and the modulus is within a specific range, a hose for fluids having excellent ozone resistance and extraction resistance can be obtained.

[0014] That is, the gist of the present invention lies in the following [1] to [5].

[0015] [1] A hose for fluids, which is formed of a nitrile rubber composition mainly composed of a nitrile rubber (A), wherein,

[0016] The modulus (M10) of the nitrile rubber composition is 0.1 to 0.5 MPa,

[0017] The nitrile rubber composition does not contain paraffin wax.

[0018] [2] The hose for fluids according to [1], wherein the nitrile rubber (A) contains polyvinyl chloride.

[0019] [3] The hose for fluids according to [1] or [2], wherein the nitrile rubber composition contains carbon black (B).

[0020] [4] The hose for fluids according to [3], wherein the content of the carbon black (B) is 10 to 150 parts by mass with respect to 100 parts by mass of the nitrile rubber (A).

[0021] [5] The hose for fluids according to [3] or [4], wherein the average particle size of the carbon black (B) is 15 to 75 nm.

[0022] Effects of the Invention

[0023] According to the present invention, a hose for fluids excellent in ozone resistance and extraction resistance can be provided. Description of the Drawings

[0024] Figure 1 is a view showing an example of the hose for fluids according to the present invention. Detailed Description of the Invention

[0025] Hereinafter, based on the examples of the embodiments of the present invention, the present invention will be described in more detail, but the present invention is not limited to these embodiments.

[0026] Hereinafter, each component contained in the nitrile rubber composition forming the hose for fluids of the present invention will be described.

[0027] [Nitrile Rubber (A)]

[0028] As the nitrile rubber (A), for example, acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (H-NBR), a blend polymer of acrylonitrile-butadiene rubber and polyvinyl chloride (PVC) (NBR-PVC), etc. can be cited. They can be used alone or in combination of two or more.

[0029] The acrylonitrile content (AN content) of the nitrile rubber (A) is generally 15 to 48% by mass, preferably 15 to 35% by mass. That is, if the AN content of the nitrile rubber (A) is less than the above range, there is a tendency for the oil resistance property to deteriorate. On the contrary, if the AN content of the nitrile rubber (A) exceeds the above range, there is a tendency for the cold resistance, etc. to decrease.

[0030] From the viewpoint of ozone resistance, the nitrile rubber (A) preferably contains PVC. That is, the nitrile rubber (A) preferably contains a blend polymer with PVC (NBR-PVC).

[0031] The content of PVC in the NBR-PVC is not particularly limited. Considering general ozone resistance, it is preferably 15 to 45% by mass in the NBR-PVC. That is, if the content of PVC is less than 15% by mass, there is a tendency for poor ozone resistance. If the content of PVC is greater than 45% by mass, there is a tendency for problems to occur in terms of processability, etc.

[0032] In the present invention, as the rubber component, a rubber other than the nitrile rubber (A) may be contained. Preferably, 80% by mass or more of the rubber component of the nitrile rubber composition is the nitrile rubber (A). More preferably, 90% by mass or more of the rubber component is the nitrile rubber (A). Further preferably, the rubber component consists only of the nitrile rubber (A).

[0033] In addition, the nitrile rubber (A) is the main component of the nitrile rubber composition. Here, the main component means a component that has a great influence on the properties of the nitrile rubber composition, and the content of this component is generally 30% by mass or more of the nitrile rubber composition, preferably 40% by mass or more, more preferably 45% by mass or more.

[0034] The nitrile rubber composition preferably contains carbon black (B).

[0035] <Carbon black (B)>

[0036] As the carbon black (B), there is no particular limitation. For example, furnace black (furnace carbon black) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF can be mentioned; acetylene black (acetylene carbon black); thermal cracking black (thermal cracking carbon black) such as FT and MT; channel black (channel carbon black) such as EPC, MPC, and CC; graphite, etc. They can be used alone or in combination of two or more. Among them, furnace black is preferred, and SRF and GPF are more preferred. By using the furnace black, there is a tendency for the modulus described later to be in a specific range.

[0037] The average particle size of carbon black (B) is preferably 100 nm or less, more preferably 90 nm or less, and still more preferably 75 nm or less. The lower limit is not particularly specified, and is preferably 15 nm or more. By making the average particle size of carbon black (B) within the above range, there is a tendency for the modulus described later to be within a specific range, and there is a tendency for excellent ozone resistance. In addition, the average particle size of carbon black (B) can be measured by using TEM or the like.

[0038] The dibutyl phthalate (DBP) absorption of the carbon black (B) is preferably 40 to 250 ml / 100 g, more preferably 50 to 200 ml / 100 g, and particularly preferably 50 to 160 ml / 100 g. By making the DBP absorption of the carbon black (B) within the above range, there is a tendency for the modulus described later to be within a specific range, and there is a tendency for excellent ozone resistance.

[0039] The DPB absorption can be measured for a non-compressed sample in accordance with JIS K6217-4 (2017).

[0040] The content of the carbon black (B) is preferably 5 to 200 parts by mass, more preferably 20 to 150 parts by mass, still more preferably 30 to 130 parts by mass, and particularly preferably 35 to 110 parts by mass with respect to 100 parts by mass of the nitrile rubber (A). If the content of the carbon black (B) is within the above range, there is a tendency to more preferably obtain the effects of the present invention.

[0041] Within a range not impairing the effects of the present invention, compounding agents commonly used in the rubber industry such as a plasticizer, a vulcanizing agent, a vulcanization accelerator, a vulcanization aid, a processing aid, an anti-aging agent, a filler other than carbon black (B), and a silane coupling agent can be kneaded in the nitrile rubber composition, for example. They can be used alone or in combination of two or more.

[0042] 〔Plasticizer〕

[0043] Examples of the plasticizer include polyester-based plasticizers, phthalic acid-based plasticizers, adipic acid-based plasticizers, and the like. They can be used alone or in combination of two or more. Among them, adipic acid-based plasticizers are preferred.

[0044] As the adipic acid-based plasticizer, for example, a plasticizer having both an ether bond and an ester bond in one molecule can be cited. Specifically, an adipic acid ether ester-based plasticizer such as bis[2-(2-butoxyethoxy)ethyl] adipate can be cited. In addition, as commercially available products of the ether ester-based plasticizer, for example, ADK CIZER RS-107, ADK CIZER RS-700, ADK CIZER RS-735, ADK CIZER RS-830, ADK CIZER RS-966, ADK CIZER RS-1000 (manufactured by ADEKA Corporation); polysulfide rubber (Thiokol) TP-95, polysulfide rubber TP-759 (manufactured by HALLSTAR Company), etc. can be cited.

[0045] When using the plasticizer, its content is usually 10 to 60 parts by mass, preferably 20 to 40 parts by mass, based on 100 parts by mass of the nitrile rubber (A).

[0046] 〔Vulcanizing agent〕

[0047] As the vulcanizing agent, for example, sulfur, a peroxide vulcanizing agent (peroxide vulcanizing agent), etc. can be used alone or in combination. Among them, sulfur is preferred in consideration of storage stability and cost.

[0048] As the peroxide vulcanizing agent, examples thereof include 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-hexylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)cyclododecane, 1,1-bis(tert-butylperoxy)cyclohexane, 2,2-bis(tert-butylperoxy)octane, n-butyl-4,4-bis(tert-butylperoxy)butane, n-butyl-4,4-bis(tert-butylperoxy)valerate and other peroxide ketals, di-tert-butyl peroxide, dicumyl peroxide, tert-butylcumyl peroxide, α,α'-bis(tert-butylperoxy)m-isopropylbenzene, α,α'-bis(tert-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hex-3-yne and other dialkyl peroxides, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, m-toluoyl peroxide and other diacyl peroxides, tert-butyl peracetate, tert-butyl perisobutyrate, tert-butyl per-2-ethylhexanoate, tert-butyl perlaurate, tert-butyl perbenzoate, di-tert-butyl m-phthalate, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, tert-butyl permaleate, tert-butyl perisopropyl carbonate, cumyl peroctoate and other peroxide esters, tert-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 1,1,3,3-tetramethylbutyl peroxide and other hydroperoxides, etc. They can be used alone or in combination of two or more. Among them, from the aspect of no odor problem, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane is preferably used.

[0049] When sulfur is used as the vulcanizing agent, its content is preferably in the range of 0.1 to 15 parts by mass, particularly preferably in the range of 0.3 to 3 parts by mass, based on 100 parts by mass of the nitrile rubber (A).

[0050] In addition, when a peroxide vulcanizing agent is used as the vulcanizing agent, its content is preferably in the range of 1.5 to 20 parts by mass, particularly preferably in the range of 5 to 10 parts by mass, based on 100 parts by mass of the nitrile rubber (A). If the content of the vulcanizing agent is too small, vulcanization is insufficient and there is a tendency for the strength of the hose to deteriorate. If the content of the vulcanizing agent is too large, it becomes too hard, and in addition to the tendency for the softness of the hose to deteriorate, there is also a tendency for the scorch time to become shorter and the processability to deteriorate.

[0051] 〔Vulcanization accelerator〕

[0052] As the vulcanization accelerator, for example, thiazole-based, sulfenamide-based, thiuram-based, aldehyde-amine-based, aldehyde-amine-based, guanidine-based, thiourea-based vulcanization accelerators, etc. can be cited. They can be used alone or in combination of two or more. Among them, from the aspect of excellent vulcanization reactivity, sulfenamide-based vulcanization accelerators and thiuram-based vulcanization accelerators are preferred.

[0053] As the thiazole-based vulcanization accelerator, for example, dibenzothiazole disulfide (DM), 2-mercaptobenzothiazole (M), sodium salt of 2-mercaptobenzothiazole (NaMBT), zinc salt of 2-mercaptobenzothiazole (ZnMBT), etc. can be cited. They can be used alone or in combination of two or more. Among them, from the aspect of excellent vulcanization reactivity, dibenzothiazole disulfide (DM) and 2-mercaptobenzothiazole (M) are preferred.

[0054] As the sulfenamide-based vulcanization accelerator, for example, N-oxydiethylene-2-benzothiazole sulfenamide (NOBS), N-cyclohexyl-2-benzothiazole sulfenamide (CM), N-tert-butyl-2-benzothiazole sulfenamide (BBS), N,N'-dicyclohexyl-2-benzothiazole sulfenamide, etc. can be cited. They can be used alone or in combination of two or more.

[0055] As the thiuram vulcanization accelerator, for example, tetramethylthiuram disulfide (TT), tetraethylthiuram disulfide (TET), tetrabutylthiuram disulfide (TBTD), tetra(2-ethylhexyl)thiuram disulfide (TOT), tetrabenzylthiuram disulfide (TBZTD), etc. can be cited. They can be used alone or in combination of two or more.

[0056] When using the vulcanization accelerator, its content is usually 0.1 to 10 parts by mass, preferably 0.5 to 6 parts by mass, based on 100 parts by mass of the nitrile rubber (A).

[0057] 〔Vulcanization aid〕

[0058] As the vulcanization aid, examples thereof include triallyl isocyanurate, N,N'-m-phenylene bismaleimide, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, isodecyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, 2-ethoxyethyl methacrylate, tetrahydrofurfuryl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, methacryloyloxyethyl phosphate, 1,4-butanediol diacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, trimethylolethane trimethacrylate, trimethylolpropane trimethacrylate, allyl glycidyl ether, N-hydroxymethyl methacrylamide, 2,2-bis(4-methacryloxypolyethoxyphenyl)propane, aluminum methacrylate, zinc methacrylate, calcium methacrylate, magnesium methacrylate, 3-chloro-2-hydroxypropyl methacrylate, zinc oxide of one kind, zinc oxide of two kinds, zinc oxide of three kinds, fine zinc oxide and the like, and magnesium oxide and the like. The vulcanization aid can be used alone or in combination of two or more.

[0059] When using the vulcanization aid, its content is usually 0.05 to 15 parts by mass, preferably 0.1 to 10 parts by mass, more preferably 1 to 8 parts by mass, based on 100 parts by mass of the nitrile rubber (A).

[0060] [Processing aid]

[0061] As the processing aid, examples thereof include fatty acids such as oleic acid, palmitic acid, stearic acid; fatty acid metal salts such as zinc laurate, zinc stearate, barium stearate, calcium stearate; fatty acid esters; and diols such as ethylene glycol, polyethylene glycol. The processing aid can be used alone or in combination of two or more. Among them, fatty acids are preferred, and stearic acid is more preferred.

[0062] When using the processing aid, its content is usually 0.2 to 10 parts by mass, preferably 0.3 to 5 parts by mass, based on 100 parts by mass of the nitrile rubber (A).

[0063] [Anti-aging agent]

[0064] Examples of the anti-aging agent include amine-ketone anti-aging agents, imidazole anti-aging agents, amine anti-aging agents, phenolic anti-aging agents, sulfur anti-aging agents, phosphorus anti-aging agents, etc. The anti-aging agent can be used alone or in combination of two or more.

[0065] When using the anti-aging agent, its content is usually 1 to 10 parts by mass, preferably 2 to 8 parts by mass, based on 100 parts by mass of the nitrile rubber (A).

[0066] 〔Wax〕

[0067] The wax as described is a wax other than paraffin wax.

[0068] Generally, paraffin wax is added to endow the nitrile rubber with ozone resistance. However, in the case where the fluid of the rubber hose for fluid use contains paraffin wax and the fluid is a low-molecular-weight oil or the like, there is a tendency for the paraffin wax to be easily dissolved. Therefore, the nitrile rubber composition used in the present invention does not contain paraffin wax.

[0069] Examples of the wax include petroleum waxes such as microcrystalline wax; natural waxes such as vegetable waxes and animal waxes; synthetic waxes such as polymers of ethylene, propylene, etc. These waxes can be used alone or in combination of two or more. However, in the present invention, from the viewpoint of extraction resistance, it is preferred that the nitrile rubber composition does not contain wax.

[0070] 〔Filler other than carbon black (B)〕

[0071] Examples of the filler other than the carbon black (B) include inorganic fillers such as silica, calcium carbonate, basic magnesium carbonate, clay, hectorite, diatomaceous earth; organic fillers such as recycled rubber and powdered rubber. The fillers can be used alone or in combination of two or more.

[0072] When using the filler other than the carbon black (B), its content is usually 5 to 200 parts by mass, preferably 20 to 100 parts by mass, based on 100 parts by mass of the nitrile rubber (A).

[0073] <Manufacturing method>

[0074] The nitrile rubber composition can be prepared, for example, by kneading the nitrile rubber (A) together with the carbon black (B), plasticizer, vulcanizing agent, vulcanization accelerator, vulcanization aid, processing aid, anti-aging agent, etc. as required using a kneader, Banbury mixer, roll or other kneading machines.

[0075] When the nitrile rubber composition is made into a vulcanized rubber sheet with a thickness of 2 mm, the modulus (M10) is as low as 0.1 to 0.5 MPa. Such a low modulus is important from the aspect of ozone resistance, and preferably 0.2 to 0.49 MPa. By making the modulus (M10) within the above range, excellent ozone resistance can be achieved. In addition, when the modulus (M10) is lower than the above range, the sealing performance of the fastening part of the joint is reduced.

[0076] In the present invention, it is speculated that by setting the modulus (M10) within a specific low range, the force (stress) exerted on the rubber material from the outside when displacement is applied can be suppressed, so the ozone resistance is excellent.

[0077] The modulus (M10) can be measured as follows.

[0078] The nitrile rubber composition is press-molded using a press vulcanizer to produce a vulcanized rubber sheet with a thickness of 2 mm.

[0079] Next, taking the vulcanized rubber sheet as a sample, a tensile test is carried out in accordance with JIS K6251-2017 (Vulcanized rubber and thermoplastic rubber - Method for determining tensile properties), and the median value of the stress (MPa) at an elongation of 10% is read as the modulus (M10).

[0080] In order to make the modulus of the nitrile rubber composition within the above range, for example, methods such as using carbon black with an average particle size within a specific range, using carbon black with a DBP absorption amount within a specific range, and making the carbon black content within a specific range can be cited. By using these methods alone or in combination of two or more, there is a tendency to make the modulus of the nitrile rubber composition within the above range. Among them, the method of using carbon black with an average particle size within a specific range is preferred.

[0081] Carbon black with an average particle size within a specific range has excellent reinforcing properties for rubber, so the stress design of the modulus (M10) can be carried out with a smaller carbon black content.

[0082] In addition, the fluid hose of the present invention can be produced as follows, for example. That is, the nitrile rubber composition is prepared, extruded into a cylindrical shape using a single-screw extrusion molding machine, and then heated and vulcanized (crosslinked) under predetermined conditions, whereby, for example, Figure 1 a fuel hose with a single-layer structure as shown can be produced. In addition, during the above extrusion molding, a mandrel can also be used as needed.

[0083] The fluid hose of the present invention is not limited to the single-layer structure as described above. If necessary, a resin layer, a reinforcing wire layer, a layer formed of other rubber compositions, etc. may be formed on the outer periphery of the hose having the single-layer structure. Further, in the case of producing a fluid hose composed of such multiple layers, the layer formed of the crosslinked product of the nitrile rubber composition of the present invention is preferably used as the layer (innermost layer) in contact with the fluid, but is not limited thereto, and may also be an intermediate layer or an outermost layer.

[0084] The inner diameter of the hose of the fluid hose of the present invention thus obtained is preferably in the range of 2 to 100 mm, more preferably in the range of 5 to 50 mm. Further, the hose wall thickness is preferably in the range of 0.5 to 20 mm, more preferably in the range of 1 to 10 mm.

[0085] The fluid hose of the present invention can be applied to, for example, transportation machinery such as automobiles, airplanes, railways, forklifts, forklift trucks, and cranes. Among them, it can be suitably used as a hose for transporting fluids used in automobiles. Specifically, for example, it can be used for fuel hoses, oil hoses, radiator hoses, heater hoses, air-conditioning hoses, etc., and cooling hoses for battery packs for electric vehicles and fuel cell vehicles.

[0086] Examples

[0087] Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited by any of the following examples.

[0088] First, before the examples and comparative examples, the materials shown below were prepared.

[0089] 〔Nitrile rubber (A)〕

[0090] · Krynac 3370 (manufactured by ARLANXEO Corporation, NBR, AN content: 33% by mass)

[0091] · Nipol 1203W (manufactured by Zeon Corporation, NBR-PVC, AN content: 32% by mass, PVC content: 29% by mass)

[0092] 〔Carbon black (B)〕

[0093] · Seast V (manufactured by Tokai Carbon Co., Ltd., DBP absorption amount: 87 ml / 100 g, average particle diameter: 62 nm)

[0094] · VULCUN 6J (manufactured by Cabot Japan Co., Ltd., DBP absorption amount: 115 ml / 100 g, average particle diameter: 22 nm)

[0095] · SPHERON 5200 (manufactured by Cabot Japan, DBP absorption: 125 ml / 100 g, average particle size: 62 nm)

[0096] · Seast S (manufactured by Tokai Carbon Co., Ltd., DBP absorption: 68 ml / 100 g, average particle size: 66 nm)

[0097] · Seast G-116HM (manufactured by Tokai Carbon Co., Ltd., DBP absorption: 158 ml / 100 g, average particle size: 38 nm)

[0098] 〔Plasticizer〕

[0099] ADK CIZER RS-107 (manufactured by ADEKA, ether ester plasticizer)

[0100] 〔Vulcanizing agent〕

[0101] · Sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd.)

[0102] 〔Vulcanization accelerator〕

[0103] · Sanceler CM-G (manufactured by Sanshin Chemical Industry Co., Ltd.)

[0104] · Sanceler TET-G (manufactured by Sanshin Chemical Industry Co., Ltd.)

[0105] 〔Vulcanization aid〕

[0106] · Zinc oxide (manufactured by Mitsui Mining & Smelting Co., Ltd.)

[0107] 〔Processing aid〕

[0108] · Stearic acid (manufactured by Kao Corporation)

[0109] 〔Antioxidant〕

[0110] · NOCRAC B (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0111] · ANTAGE NBC (manufactured by Kawaguchi Chemical Industry Co., Ltd.)

[0112] 〔Wax〕

[0113] · SUNTIGHT R (manufactured by Seiko Chemical Co., Ltd.)

[0114] 〔Examples 1 - 6, Comparative Examples 1 - 3〕

[0115] Mix the components other than the vulcanizing agent and vulcanization accelerator in the proportions shown in Table 1 below, and knead them using a Banbury mixer. Then, mix the vulcanizing agent and vulcanization accelerator in the proportions shown in Table 1 below, and mix them using rolls to prepare a nitrile rubber composition.

[0116] In addition, subject each of the obtained nitrile rubber compositions to pressure molding using a compression vulcanizer to produce a vulcanized rubber sheet with a thickness of 2 mm. Use this vulcanized rubber sheet to evaluate each property according to the following criteria. These results are shown together in Table 1 below.

[0117] <Modulus (M10)>

[0118] Using the vulcanized rubber sheet, conduct a tensile test in accordance with JIS K6251-2017 (Vulcanized rubbers and thermoplastic rubbers - Determination of tensile properties), and read the median value of the stress (MPa) at 10% elongation as the modulus (M10).

[0119] <Ozone resistance>

[0120] Using the vulcanized rubber sheet, conduct a static ozone degradation test in accordance with JIS K6259-1 (Vulcanized rubbers and thermoplastic rubbers - Methods for determining ozone resistance - Part 1: Static ozone degradation test and dynamic ozone degradation test) under the conditions of a test temperature of 40°C, an ozone concentration of 50 ppm, and a tensile strain of 10%, visually confirm whether cracks have occurred on the vulcanized rubber sheet, and evaluate it according to the following evaluation criteria.

[0121] [Evaluation criteria]

[0122] Excellent: No cracks occurred until 168 hours later

[0123] Very good: No cracks occurred until 48 hours later

[0124] Good: No cracks occurred until 24 hours later

[0125] Poor: Cracks occurred before reaching 24 hours

[0126] <Extractability resistance>

[0127] Cut the vulcanized rubber sheet into a rubber sheet with a side length of 7 mm and collect 6 g of it. Put it into a test container, add 25 mL of test oil (isooctane), keep it at a test temperature of 80 °C for 70 hours, and then let it stand at room temperature (25 °C) for 24 hours. After standing, take out the rubber sheet from the test oil (isooctane), transfer 10 mL of the test solution to a centrifuge tube, let it stand in a cooling bath at -15 °C for 5 hours, and then centrifuge it at 1900 rpm for 30 minutes. Then, read the volume (mL) of the precipitate at the bottom of the test tube, calculate the amount of precipitate from the following formula, and evaluate it according to the following evaluation criteria.

[0128] Amount of precipitate (volume %) = Volume of precipitate (mL) / Test solution (10 mL) × 100

[0129] [Evaluation criteria]

[0130] Very good: The amount of precipitate is 1 volume % or less

[0131] Good: The amount of precipitate is greater than 1 volume % and less than 2 volume %

[0132] Poor: The amount of precipitate is 2 volume % or more

[0133]

[0134] According to the results in Table 1 above, the ozone resistance and extraction resistance of each nitrile rubber composition of Examples 1 to 6 are excellent.

[0135] In contrast, each nitrile rubber composition of Comparative Example 1 and Comparative Example 3 with a modulus greater than 0.5 MPa results in poor ozone resistance and cannot balance ozone resistance and extraction resistance.

[0136] In addition, in Comparative Example 2, due to the use of paraffin wax, the result is poor extraction resistance and it cannot balance ozone resistance and extraction resistance.

[0137] From the above, it can be seen that when manufacturing a fluid hose from each nitrile rubber composition of Examples 1 to 6 by a known method, the resulting fluid hose has excellent ozone resistance and extraction resistance.

[0138] In addition, in the above embodiments, specific modes of the present invention are shown, but the above embodiments are merely examples and are not to be construed in a limiting sense. Various modifications obvious to those skilled in the art are intended to be within the scope of the present invention.

[0139] Industrial applicability

[0140] The fluid hose formed from the nitrile rubber composition of the present invention can be suitably used for, for example, transportation machinery such as automobiles, airplanes, railways, forklifts, forklift trucks, cranes, etc. because of its excellent ozone resistance and extraction resistance.

Claims

1. A fluid hose, comprising a nitrile rubber composition comprising a nitrile rubber (A) as a main component, wherein: The modulus (M10) of the nitrile rubber composition is 0.1 to 0.5 MPa, The nitrile rubber composition does not contain paraffin wax.

2. The fluid hose according to claim 1, wherein, The nitrile rubber (A) contains polyvinyl chloride.

3. The fluid hose according to claim 1 or 2, wherein: The nitrile rubber composition contains carbon black (B).

4. The fluid hose according to claim 3, wherein, The content of the carbon black (B) is 10 to 150 parts by mass based on 100 parts by mass of the nitrile rubber (A).

5. The fluid hose according to claim 3 or 4, wherein, The average particle size of the carbon black (B) is 15 to 75 nm.

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